JPG and PNG decoder

[cal]

On Sunday, 17 June 2012 at 12:15:36 UTC, bearophile wrote:
> Suggestions on the code:
> - Try to use final switches.
> - switch cases don't need (), so instead of case(foo):  write 
> case foo:
> - Try to add const/immutable/pure/nothrow where possible.
>
> Bye,
> bearophile

Problem with final switches in this context is that images may be 
corrupt or badly encoded or something, which the decoder should 
just handle gracefully through a default I think, without 
crashing. The case statements though I will change, and though I 
have worlds of trouble with const-ness, I will endeavour to add 
those guarantees :)

Thanks for looking through